Exhaust gas turbochargers are provided on an engine to deliver air to the engine intake at a greater density than would be possible in a normal aspirated configuration. Turbochargers typically include a turbine housing connected to the exhaust manifold of the engine, a compressor housing connected to the intake manifold of the engine, and a bearing housing coupled between the turbine and compressor housings. A turbine wheel in the turbine housing is rotatably driven by an inflow of exhaust gas supplied from the exhaust manifold. A shaft rotatably supported in the bearing housing connects the turbine wheel to a compressor impeller in the compressor housing so that rotation of the turbine wheel causes rotation of the compressor impeller. Rotation of the compressor impeller increases the air mass flow rate, airflow density and air pressure delivered to cylinders of the engine via the intake manifold.
Thus, turbochargers deliver compressed air to an engine allowing fuel to combust more efficiently. A diesel engine operates at higher air-to-fuel ratios with higher efficiency compared to other engine cycles. Turbocharging is an efficient approach to increasing air-to-fuel ratio for the diesel engine combustion cycle. In the case of other engine configurations and combustion cycles, turbocharging is an effective method for increasing power density. An increase in power density allows the use of smaller, lighter engines at similar power levels. The use of a smaller engine in a vehicle decreases the mass of the vehicle, increases performance, and enhances fuel economy. Moreover, turbochargers provide a more complete combustion of the fuel delivered to the engine, which reduces engine emissions.